1. Field of the Invention
The present invention relates to an optical apparatus including an image stabilizing apparatus which detects vibration (shaking) generated in the optical apparatus or the like, and causes a lens (image stabilizing unit) to move in a direction perpendicular to an optical axis while detection of the vibration is used as information for image blur correction, to thereby correct an image blur.
2. Description of the Related Art
In a camera, nowadays, because operations such as exposure determination and focusing important for photographing are all automated, a risk that those unskilled in camera operation may fail in photographing has been greatly reduced. In addition, in recent years, studies have been conducted on a system which corrects an image blur caused by shaking applied to the camera. Accordingly, there are now almost no factors to cause photographers to fail in photographing.
Here, the system that corrects the image blur caused by shaking is described briefly.
Shaking of the camera during photographing is normally a vibration with a frequency of from 1 Hz to 12 Hz. In order to enable photographing free of the image blur even when the shaking occurs at the time of shutter release operation, basically, a camera vibration due to the shaking must be detected, and then a correction lens must be displaced according to the detection value. Therefore, in order to enable photographing free of the image blur even when the shaking occurs, first, it is necessary to detect the camera vibration accurately. Second, it is necessary to correct an optical axis change caused by the camera vibration through displacing the correction lens.
In principal, detection of the vibration (shaking) can be performed through installing into the camera a vibration detecting unit for detecting acceleration, angular velocity, or the like, and a camera shake detecting unit for electrically integrating a signal output from the vibration detecting unit and outputting displacement. Through controlling the image stabilizing unit which is installed in the image stabilizing apparatus to displace the correction lens based on the detected information and to change the optical axis in photographing, the image blur correction can be performed.
Here, an outline of an image stabilizing system is described, which uses a shake detecting unit and suppresses an image blur caused by vertical camera shake (pitch direction) and lateral camera shake (yaw direction).
The image stabilizing system includes a lens barrel, the shake detecting unit for detecting the vertical camera shake and the lateral camera shake, a image stabilizing optical unit, a coil for imparting a thrust force to the image stabilizing optical unit, and a detection element for detecting a position of the image stabilizing optical unit. The image stabilizing optical unit is driven by an electromagnetic actuator formed of a coil and a magnet. Further, the image stabilizing optical unit includes a position control loop, and is driven while using output of the shake detecting unit as a target value, to thereby secure stability in imaging position on an image plane.
Further, in the image stabilizing apparatus, there is often provided a rolling prevention structure for moving the image stabilizing optical unit only in the pitch direction and the yaw direction to prevent the image stabilizing apparatus from being rotated. This is because, when rolling occurs besides movement in the pitch direction and the yaw direction, a position detecting unit detects a moving amount different from an actual blur correction amount to perform false correction based on a false signal such as so-called crosstalk, with the result that precise image blur correction cannot be performed.
The applicant of the present invention also has already proposed the following structure as the rolling prevention structure.
In Japanese Patent Application Laid-Open No. H10-197911, there is proposed an optical image stabilizing apparatus in which rotation of a correction lens about the optical axis is prevented with use of an L-shaped guide shaft. However, in the optical image stabilizing apparatus disclosed in Japanese Patent Application Laid-Open No. H10-197911, a guide mechanism for preventing rotation of the correction lens about the optical axis is configured to guide the correction lens so that the correction lens parallelly moves while sliding. Therefore, there is a problem in that sliding friction generated in the guide mechanism deteriorates driving responsibility during, in particular, micro driving of the correction lens.
In this context, in Japanese Patent Application Laid-Open No. 2004-101721, there is disclosed an optical image stabilizing apparatus in which rotation of a correction lens about the optical axis is suppressed with use of rollable balls. The optical image stabilizing apparatus includes a guide member having V-shaped groove portions formed in both surfaces thereof and extending in directions orthogonal to each other. In addition, the optical image stabilizing apparatus includes balls (steel balls) arranged in the V-shaped groove portions on one surface of the guide member to be interposed between the guide member and a base member of the optical image stabilizing apparatus, and balls arranged in the V-shaped groove portions on the other surface of the guide member to be interposed between the guide member and a lens holding member for holding the correction lens.
Similarly, a rolling prevention structure using rolling balls is disclosed in Japanese Patent Application Laid-Open No. 2008-185643. Owing to the rolling prevention structure, rolling can be reliably prevented even when high-frequency vibration is generated or a large external force is applied.
In each of Japanese Patent Application Laid-Open No. 2004-101721 and Japanese Patent Application Laid-Open No. 2008-185643, the rolling prevention structure using rolling balls is proposed. The rolling balls and the guide member serving as the rolling prevention structure are overlaid in an optical axis direction. Further, biasing units provided to obtain a rolling prevention effect owing to the rolling balls are arranged to be opposed to each other through a rolling prevention structure section and an image stabilizing unit. Thus, the image stabilizing apparatus itself is enlarged in size in the optical axis direction, and imposes restrictions on optical designing. Further, a large number of components are overlaid on a fixed member, and hence it is essential to increase dimensional accuracy of each component in order to obtain positional accuracy in the optical axis direction of an image stabilizing optical system, which is disadvantageous in terms of manufacturing cost of the components.
Further, in an embodiment of Japanese Patent Application Laid-Open No. 2008-185643, the image stabilizing optical system of the image stabilizing apparatus is supported in the optical axis direction by rolling balls other than rolling balls serving as the rolling prevention structure, and hence the positional accuracy in the optical axis direction is easily obtained. However, no fewer than nine rolling balls are required, and the biasing units and the rolling prevention structure are arranged to be overlaid on each other in the optical axis direction. Thus, there is a problem in that the image stabilizing apparatus itself is further enlarged in size in the optical axis direction. Further, a large number of components are required, and hence there is a problem in assembling property.
The present invention has been made in view of the above-mentioned problems, and therefore it is an object of the present invention to provide an optical apparatus including an image stabilizing apparatus in which the rolling prevention structure is formed of rolling balls so that the image stabilizing apparatus guides a lens with less frictional resistance and has a compact configuration, and in which the assembling property is improved, and the positional accuracy in the optical axis direction of the image stabilizing optical system is increased.